<h3>1.描述</h3>
<p>
  场景测试：在有textarea的页面，且textarea的宿主元素初始display:none,
  页面有滚动条时，将页面滚动条拖至formfiled的头部不在视野范围内时，textarea动态显示时页面滚动条会异常跳动到顶部。
</p>
<h3>2.示例</h3>
<ti-formfield [verticalAlign]="'middle'">
  <ti-item [label]="'测试'" *ngFor="let item of items">
    <span>item1</span>
  </ti-item>
  <ti-item [required]="item1.required" [show]="item1.show" [index]="99">
    <ti-item-label> ewdfwew</ti-item-label>
    <ti-switch style="width: 42px" [(ngModel)]="enableWhiteList"></ti-switch>
  </ti-item>
  <ti-item [show]="enableWhiteList" [required]="item2.required" [index]="100">
    <ti-item-label> wqwqw</ti-item-label>
    <textarea tiTextarea style="width: 220px; height: 100px" resize="vertical"></textarea>
  </ti-item>
</ti-formfield>
